I think it was already pretty well known there was water on mars, just not flowing as a liquid, which is why they think it is salty brine which has a low freezing temp. There was a statement made about the salinity being about what our oceans are, but can our oceans stand temperatures that low? And that low an atmospheric pressure? Granted, the flow didn't go very far before it either evaporated or absorbed into the soil but couldn't the main idea be tested on Earth in a vacuum chamber?